Question

chimpanzees exhibit 99% genetic similarity to humans. cows share approximately 80% of their dna sequence with humans. scientists can predict the relative age of a common ancestor using dna sequences. which of the following statements regarding molecular clocks is true?
○ molecular clocks cannot provide information regarding the relatedness of organisms or how distantly related common ancestors are from descendant species.
○ cows do not share a common ancestor with chimpanzees and humans, and any genetic relatedness is by chance.
○ the common ancestor of chimpanzees and humans lived more recently than the common ancestor of cows, chimpanzees, and humans.
○ chimpanzees, humans, and cows were at one time more closely related, but due to genetic drift have become more distantly related from one another.
○ the common ancestor of cows, chimpanzees, and humans lived more recently than the common ancestor of chimpanzees and humans.

Explanation:

Molecular clocks use genetic similarity to infer relatedness and ancestor timing. Higher similarity (chimpanzees-humans: 99%) means a more recent common ancestor than lower similarity groups (cows with them: ~80%), so their shared ancestor is older. Other options are false: molecular clocks do show relatedness, all three share a common ancestor, and relatedness doesn’t reverse via drift.

Answer:

The common ancestor of chimpanzees and humans lived more recently than the common ancestor of cows, chimpanzees, and humans.